The brain’s electrical activity fluctuates from second to second. The routine EEG provides a 20- to 40-minute sample of brain electrical activity, which is often sufficient. In some patients with epilepsy, however, this recording is normal or shows only minor, nonspecific findings. In such cases, an extended recording that includes long periods of wakefulness and sleep is desired. For example, in some people, epilepsy waves occur only once every 3 or 4 hours or only after an hour of sleep, and a routine EEG will almost always be normal.
An ambulatory EEG, on the other hand, can record up to 72 hours of EEG activity with a special recorder that is slightly larger than a portable cassette player. This recorder allows you to go about your normal routine while the EEG is being recorded.
Your doctor may order an ambulatory EEG for you for a number of reasons:
The first day of an Ambulatory EEG set up procedure lasts one hour. The EEG technologist will attach 16 to 25 flat metal discs called electrodes to different places on your head, using a special glue called collodion to keep them in place. The electrodes are connected by wires to a small recorder that amplifies and records the electrical activity inside the brain. You can wear the recorder on your waist, with the wire running either under or outside of their shirt. For people with a full head of hair, the electrodes can be fairly well camouflaged. Even so, most of you may prefer not to go to work or school with the electrodes on their scalp.
You will be asked to keep a diary of activities during the day. Most recorders have an “event” button for patients to press if they experience any of the symptoms for which they are being tested, such as episodes of feeling “spacey” or confused. A family member should press the button if the patient is unable to do it.
An ambulatory EEG test may last anywhere from 24 to 72 hours. Please do not take a shower during this time as water will damage the machine.
An appointment will be made for the technologist to remove the electrodes from your scalp with acetone or similar solutions at the end of the test. You still may wish to wash your hair when returning home to remove any remaining paste.
The EEG has been used for many years and is considered a safe procedure. The test causes no discomfort. The electrodes only record activity and do not produce any electrical current.
Skin irritation or redness may be present at the locations where the electrodes were placed, but this will generally wear off in a few hours.